Variable pressure system



Aug. 11, 1953 R. E. MOORE VARIABLE PRESSURE SYSTEM 2 Sheets-Sheet 1 Filed June 14, 1947 z/ ATTORNE ys Aug. 11, 1953 R. E. MOORE 2,648,389

VARIABLE PRESSURESYSTEM Filed June 14, 1947 2 Sheets-Sheet -2 IN V EN TOR.

1 Richard E Mnnre BY/MWMW,

A from/E115v Patented Aug. 11, 1953 VARIABLE PRESSURE SYSTEM Richard'E. Moore, Dayton, Ohio, assigner -to'General Motors Corporation,- Detroit, Mich., aV corporation of Delaware Application .lune 14, 1947, Serial No. 754,689

14 Claims. l.

ThisV invention relates to the control ofV variablel pitch propellers, particularly those involving.4 ii'uid pressure mechanism for shifting the blade pitch to accomplish desired ends.

One ofthe objects of the invention is to reduce the amount of off-speed of a governing system. by increasingA the proportionalizing rate of a.. controly valve.

Another objectofthe invention is to provide a propeller control by which the propeller speeds are, caused to follow closely and quickly, acceleration and deceleration of the drivingforce.

AnotherA object ofthe invention is to maintain. theA source pressure at a fixed amount above the pressure necessitated for operating one of` the.` pitch control functions. A further. object of the invention is to provide a fluid pressure system of' the' variable pressureY type. that. will maintain a constant rate of decrease pitch change for flow-sensitive systems.

A. further object of' the invention is to provde a fluidpressure system that will maintain desirable rates. of pitch change though subjectedito. extreme demands of iiow for eiecting a. pitch. change; function.

A further. object of the invention is to provide a fluid'pressure systeml of the variable pressure. type having a pressure relief that will maintain a consistent rate of pitch change for flow sensitive systems'.

A further. object is to provide a fluid pressure system and control apparatus therefor that will maintain the required pressure against the ever present blade load tending to shift to a predetermined position.

Still another object of the invention is to providea governor controlled fluid pressure system of high potential, in which the governor becomes atruev iiow governor and only throttles pressure fluid through one portl during normal operation, thereby removing all reversing flow forces from the governor valve, and maintaining aA constant pressure drop across the governor. Another object of the invention is to improve the` system disclosed in my copending applicationSer. No. 718,071, now U. S. Patent Serial No. 2,536,138, issued January 2, 1951, by providing a governing system in which pressure fluid is. throttled. through Vbut one port for all conditions. of operation.

Yet another object of the invention is to provide a fluid pressure system for the controlA of variabley pitch propellers, which system will have maximum. pressure sensitivity as well as produce an ideal constant pressure dinerential between source pressure and increase pitch port pressure.

Among other objects of the invention is to provide a fluid pressure system of control for variable pitch propellers whose blades havehigh centrifugal twisting moments tending to decrease pitch, and in which the centrifugal twisting moment varies as the square of the rotational speed and which may become critical at Very low rotational speeds of operation.

The indicated objects and advantages are accomplished by providing a pressure control unit of three element structure that incorporates an equal area valve operating in the nature of a pressure control valve which isr constantly conneeted with a pump source and operates to meter flow through the increased pitch porty of the governor valve and apply the pressure potential of that port to a constant-leak valve as a second element of the unit, and which operates to-maintain a constant pressure differential between the increased pitch port of the governor and a pressure source. The third element of the unit is a relief valve constantlyl exposed to the source pressure for safe-guarding the system. A. pressure reducer Valve interposed in. the, decrease pitch line maintains a constant decrease pitch pressure by tapping into the line of. pressure source instead of metered application through a governor port, while oiering no restriction of the drain from the torque unit upon increase pitch change. With the governor valve so organized as to maintain a predetermined amount of negative overlap at the increased pitch port, thena predetermined flow of hydraulic fluid is delivered to one side of the blade torque unit and to the exit orifice of the constant-leak valve. In normal, or on speed operation, the quantative factor of leak and the pressure urge on the one side of the blade torque motor balances thecentrifugal moment of rotative force on the blade tending to decrease the blade pitch, by means of which, for normal on-speed operation, the pitch of the blade is held substantially fixed for operation at the speeds selected by the governor valve.

Further objects'and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

Fig. 1 is a schematic view of the iiuid circuit for the improved variable pressure system.

Fig. 2 is a detailed view with parts in section showing the constant leak valve.

Fig. 3 is a detailed View with parts in section showing the pressure reducing valve.

Fig. 4 is a schematic view of a propeller mechanism in section showing the general distribution of the control elements and circuit of the variable pressure system.

With particular reference to Fig. 1 of the drawings, which shows schematically the hydraulic circuit, I is a pump or pressure developing means drawing hydraulic fluid from a reservoir thru an intake I2 and eeds it to a pressure delivery une I4, leading to the waist I6 between lands I8 and 20 of a governor valve 22. The governor valve incorporates a stem extension 24 of the waist I6 that pivotally connects at 26 to a lever 28 resting on a movable fulcrum 30 secured to a carriage 32, the latter being manually adjustable as will presently appear for selecting a speed at which the governor valve is to control. The

governor valve unit 22 is situated for response to centrifugal force acting toward the top of the sheet of drawing as shown in Fig. l and tending to compress a spring 34 which holds the lever 28 against the fulcrum 30, the valve plunger thereby being capable of sliding movement in a sleeve 36 providing an increased pitch port 38 vadapted to cooperate with the land I8 of the valve plunger. From the control port 38 a tubular passage 42 leads to a chamber 45 on one side of a piston element 50 contained within a Acylinder 52 constituting a blade torque unit for sidering that the propeller rotates upon an axis 64 by a shaft 66 in the direction of the arrow 68, then movement of the piston 50 toward the top of the view of Fig. l will so actuate the blade by rotating it around its pitch axis 62 as to increase its angle of attack upon the air stream, thus increasing the blade pitch.

A branch line 'I0 leading from the pump pressure line I4 opens into a chamber 'I2 forming a damping chamber 12a and pressure regulating chamber 12b for an equal-area valve 14, a secondary connection 'I6 opening from the chamber 'I2 into a pocket 'I3 into which extends a piston 80 having a fiat head 82 engaged by a spring 84 contained within a chamber 8G. The piston 80 is always subject to the pump pressure within the pocket i8 and is urged to the extended position illustrated by the spring 84 but is subject to depression by the pressure within pocket 'I8 until now is established to the drain slot 88 which will relieve an excess of pressure that may occur in the pressure lines 'I0 and I4.

The equal area Valve comprises a stem 90 having a head 92 substantially less in diameter than the bore of the chamber i2 and which is engaged by a damping washer 94 adjacent the underside of the head 92 where it is maintained by a Spring 36 engaging the bottom of the chamber 'I2 adjacent a small bore 98 which houses a valving portion of the stem 90 and from which laterally extends fluid passages as will presently appear. The stem is provided with a Valving land |00 and a valve and guide land |02 separated by a waist portion |04 and all contained within the bore 58. An axial bore |06 extending from the lower end of the stem 90 upwardly intersects one or more cross bores |08 that open thru the waste portion |64 of the valve so as to establish communication between an annular groove 0 about the stem between the lands |00, |02, and a pressure chamber H2 at the bottom of the bore 93. Communicating with the annular groove I It there is a passage ||4 that leads to a groove H6 always communicating with the increased pitch port 38 of the governor valve 22. A second passage ||8 communicating with the annular groove H0 opens into a channel |20 in the porting sleeve |22 of a constant leak Valve the flow through the passage EIS being controlled by the land |02. The porting sleeve |22 is disposed within a chamber |24 housing a plunger |26 having a landed stem |28 contained within a bore |30 of the sleeve |22, the bore |30 having cross passages |32 connecting it with the annular groove |20. Thus, it will be observed that the potential of pressure occurring at the increased pitch port 33 will always be applied through the conduit ||4 to the annular groove II, and the pressure chamber ||2, and under certain conditions to the cross passage IIB and the annular groove |20. The stem |28 provides a guide land |34 spaced from a valving land |36 separated by a waist portion |38 which is characterized like the spaced lands of the equal-area valve to connect the annular groove about the waist |38 with the lower end of the valving land through a port |40 and axial bore |42 shown in sectional detail in Fig. 2. The valve stem |28 with its land |36 cooperates with cross passages |32 to regulate the amount of hydraulic fluid moving from the passage IIB to the chamber |44 at the lower end of the stem |28, increase of pressure in the chamber |44 tending to raise the stem such that the land |36 cuts 01T the flow thru the ports |32, and being resisted by a spring |45 contained within an exhaust chamber |48 at one end of the chamber |24. The exhaust chamber |48 is ported to the outside of the valve unit at |50 and has a cross passage |52 extending from the chamber |48 and opening into the bore 98 of the equal-area valve in the region of one end of the valving land |00 of the stem 90, an extension passage |54 leading from the bore A98 into the exhaust chamber S6 of the'relief valve which has a port of exit |56. It will be observed that the passages |52 and |54 constitute drain passages for the equal-area Valve and are controlled by the valving land |00 of the stem which controls communication of these passages with the pump line pressure thru the bore 98 opening into the chamber 12.

Brieiiy, variation of pressure at the increased pitch port 30 and groove IIG of the governor 22 is applied to the conduit ||4 and to the annular groove ||0 and thence thru the opening |08 and axial bore |06 to the pressure chamber |I2. A rise or fall of pressure in ||2 tends to raise or lower the valve stem 90 lor changing the openings of the passages |52 and |54. If the pressure in chamber ||2, increases then the force applied to the valve stem 90 will assist the spring 96 and the centrifugal force of propeller rotation in covering the orifices into the passages |52 and Il'by the land |00. Ii the pressure in chamber H2, decreases, the assistance to centrifugal force and spring force upon the valve stem is removed and the pressure in chamber 12b on the annular surface of land |00 dominates and to lower the valve member 90 for opening the drain ports |52 and |54. Under those conditions the equal area valve will blow off to lower the pressure in chamber '12.

sure within the chamber 'I2 the potential Vwithin pump` linesV '|11 and I4v builds up and may beso great, i'no" regulation is provided; asV to causea blowof ofthe relief Valve thru thepcrt 882 That blowoi is`partially preventedby the potentialA of pump line pressure thru the passage and chamopeningis ofl larger diameter than the diameter of the stem- SIJthat passesfthru it. Thus, downward movementof' the valve as illustrated in Fig. li is considerably more damped than is the upward movement' because movements tending to compressvthe spring 96 keep the washer 94 in close engagement with the ange 92, whereas upward movement of the equal-area valve may tend to separate the washer 94 from the flange 92, permitting a quick or more rapid relief of the hydraulic liuid trapped in the damping chamber tEd.

A further variation in the upward movement ofV the equal area valve 90 is accomplished thru the action of the constant-leak valve |26. As heretofore stated', the pressure potential occurring at the increased pitch port 33 may be present in the annular passage and cross passages i3 and is there controlled by the valving effect of the land |36' which admits that pressure potential thru the passages |40 and |42 to the pressure chamber |44. Thus, if the pressure in |44 is increased, the land |36v will be raised to close the ports |32 which stops upward movement of the stem |28. A carefully dimensioned bleed orifice provides a constant leak thru the lines mentioned extending from the increased pitch port 38. Except for conditions hereinafter stated, there will be a continual ilow of hydraulic iluid from the pressure line I4 thru the increased pitch port 38, I 6, line I I4 and waist of the equal-area valve and constant-leak valve to exit at the port |60. Since the waist of the equal area valve, that is, the annular channel III), is always connected to the pressure chamber I2, the assisting effect applied to the spring 96 will be under the control of the constant-leak port ISI).

The relation of the passages |52, |54, and I|8 are disposed in such relation to the land H30 and |02 of the stem 95.-, that there exists at least a slight metering of the flow into the passage IIB by the time that the drain through the passages |52. and |54A is completely cut off. When the orii'lce from the bore 98 into the passage IIB is less in area than that of the bleed orifice then the rate of bleed is diminished and the pressure inchamber |44 drops because of the lessened flow of iiuid thereto. However that produces no substantial change in the pressure line over what is wrought by the diminished flow through H8. That restriction, of course, occurs only when there is a considerable and sudden drop in pressure potential within the line 10 that effects closing of the blow on ports |52 and |54. The line experiencing a sudden fall in pressure potential, the branch from the increase pressure port 38 to the constant-leak device is temporarily restricted or perhaps entirely closed off to afford a more rapid recovering of the working potential in the pressure line. Sudden build-up of pressure following those conditions is amply guarded against 'byf the' relief valve 8|l and: the pressure control Orequal-areavalve whioheopens theY orice tov |1|8 just-l as soon as thefpressure-inthe line lrwill accommodate the flow or leak fromport IBiandyet supply thevsystemv for governed opr-ration.`

Fromthe foregoing it will;be apparent` that the fluid pressure potential applied to the torque unit chamber for increasing the pitch is. always governed' high pressure whose potential. is controlled bythe provision of. aconstantleak of controlled magnitude by means of ar pressure controlling assembly-'taking into account excessive. demands of fluid'flow-Tromal bounteoussource of: supply; The volumeof fluid. delivered by the pump It. is designed to be quite in excess. of that needed for governed pitch.v operation and. to supply the constantleak through. port |60, and yethavefavailable. a sufficient supply of fluid ilow to effect feathering: and reverse pitch shift if called. for. Thai-providesfor a constant pressureapplication in the chamber 46 of the torque motor through the: ofl-set. valving relation at port 33, while the reversesideol` the-piston 5|] is constantly subject ed to anV opposing pressure of reduced potential accomplished by a pressure reducing valve |-61| inserted between thedecreased pitch line 44, and the. branch line 1li always communicating with the pump |13. The pressure reducing valve' |e| provides a chamber. |53y with an outside opening |155 and which housesa portingY sleeve |61( channeled at |59A to communicate by' bores with an axial bore |13 slidably' engaging a spool inember |15 having lands |11 and I19-on oppositesides ofa channell ISI. A head member |83 of the spool member is engaged by a spring' |85- within the chamber |63 for holdingV theV valve in depressed relation so that channel I8 will normally communicate with the bores I1I, and-by holes |81 and countersink |89- connect them with an4 end passage or chamber |9| to which the decrease pitch line 44 is connected. The channel |38. of the porting sleeve is connected by passage |93 to the pressure branch 1) suchthat the pressure therein may penetrate through passage |.93,.chan nel. |69, bores` |1I, channelV Il', holes |81 and countersink- |89V to chamber. |9| and'. thence by line 44. tothe decrease pitch. side of the torque unit. However, the full force. of the potential inline 1,0 is notv subjected to the. chamber 48. of the torque unit, because of the action of the pressure reducing. valve |5 I The potential of pressure in the line or branch 10 when. applied to the channel |8| ofthe spool member |15 hasy no eiect. because of the equal area. of the annular faces at the junctures. of the lands |11 and |19,v but since the channel |8I is connected `by the holes. |81 and countersink |89 with the end face of the land |19, the spool member |15 is thereby raised upward against the. tension of spring until the bores |1| are so far covered by the edge of land |19 that areduced ilow and consequently a reduced pressure obtains inthe chamber I9|. That reduced pressure is depended upon torestrain the blades from shifting to -decrease pitch when the governor 22 is controlling for on speed, or is in the equilibrium position.

During governor action calling for increase pitch the port 38 is more widely opened to admit the increased flow to chamber 46 and at the same time to channel I I0 of the equal area valve 14l which latter manifests in raising of the plunger 90 and cut-off of the blow-off` ports |52, |54 so' that the pressure in line I4 and 1U is raised as neededI and applied to the chamber 46V for moving the piston 50. Movement of the piston effects drain of the chamber 48 through the line 44 to the chamber |9| of the pressure reducing valve |6|, where the spool member |15 is raised against the spring |85 to cut off the bores |1| and open the notches |95 in the castellation of the porting sleeve |61 surrounding the land |11 substantially as shown in Fig. 3. The drain from the chamber 48 is thus effected through the countersink |89 from the chamber |9| to the holes |81, channel |8I, notches |95 of the castellation, chamberl |63 and opening |65. The pressure reducing valve |6| therefore acts in a dual capacity to provide a relief valve for the decrease pitch line or chamber 48.

In governed action calling for decrease pitch the port 38 is not only closed off from pressure application but the channel 220 is connected with -the port 38 so that the drain connections are set up for the chamber 46. Pressure is immediately reduced in connections 42 and ||4, the latter of which leads to the chamber ||2 of the equal area valve, which now having no assistance for the spring and centrifugal force normally acting on it to close off the blow-off ports |52 and |54, suddenly retracts so as to relieve I the pressure in branch through the ports |52,

|54, chambers 86, |48, and ports |50, |56. The diminution of pressure in branch 10 is not enough to deplete the power source for moving the piston of the torque unit. Directly that the drain starts from chamber 46, the piston 50 moves downwardly from the pressure application in chamber 48 with a sufficient reduction of pressure therein and in the chamber |9| to allow retraction of the spool member with wider opening of the bores |1| leading to the branch 10. Any flow of fluid from branch 10 immediately reflects in a new position of the equal area valve 14 to maintain the potential of the line, so that there is, on call for a decrease pitch change, a continual and satisfactory reduced pressure application to the torque unit to effect the pitch change called for.

Applying the same principles exhibited in the schematic diagram of Fig. 1, provides the sectional pictorial view of Fig. 4 where the elements shown in Fig. 1 have been distributed around the propeller shaft 66, supported by the bearings |10, carried by an engine nosing or gear casing |12, and from which the shaft rotatably extends to drivingly supporta propeller hub |14, providing sockets |16, journalling the blades 60 for pitch shiftable movement about their longer axes, and for revolution about the axis of the shaft 66. Rotatable with the shaft and hub there is a regulator comprising an annular plate |18 and a cover member |80 that cooperates to provide a reservoir |82 housing the control apparatus of Fig. 1, and here designated as the governor valve GV, a relief valve RV, andl equal area valve EAV, the constant leak valve CLV,

the pressure reducing valve PRV, and a pump or Y pressure creating device |0. These elements are so mounted upon the regulator plate I 18 as to properly take advantage of centrifugal force of rotation when considering that the regulator supporting and enclosing these elements is rotated about the propeller shaft 66 as an axis. Fluid passages extend from the pump to the various element of the control apparatus in accordance with the principles expressed with respectv to Fig. 1, the pitch increase line 42 and the pitch decrease line 44 each having branches 42a and n b and 44a and b respectively leading to the appropriate chambers 46 and 48 of the two blades here shown. Instead of the rack or gear connection between the piston and blade as shown in Fig. l, the piston 50 of Fig. 4 has splined engagement at 56a with the cylinder 52, and at 56h with a spindle |15 of the hub |14. Lineal movement of piston 50 rotates the blades 60 in its socket relative to the spindle |15 by reason of the double helical splines 56a and 56h. Each of the blades is provided with a blade gear |84 that each mesh with a master gear |86 adapted to keep the blades in track and insure that as one blade changes in pitch the other will also change in pitch an equal amount. Also included in Fig. 4 there is an accumulator |88 disposed axially of the hub |14 and providing a pressure line |90 adapted to connect into the system for use in connection with feathering and unfeathering of the propeller blade, where that function is desired. However, since the feathering function plays no particular part in the novel control of pitch that is herein described, it is not deemed necessary to enter into the description of blade feathering.

The control apparatus embodied within the regulator |86 is always under control of the pilot insofar as the governor valve GV may be set at any time to establish a speed level at which the automatic mechanism is to control. It has been stated earlier, that the fulcrum roller 30 is mounted on a movable carriage 32 for selecting a speed at which the governor valve will control and that is accomplished in Fig. 4 by supporting the carriage 32 between a pair of guide ways |92 with an extension or shoe |94 of the carriage engaging a groove |96 of a control ring |98. The control ring encircles the shaft 66 and is slidable longitudinally thereof by means of high-lead control shafts 200 threaded into the ring |98 and journaled in a ange 202 of a sleeve 204 maintained against rotation with the propeller, by means of a lug 206 engaging between brackets or clips 208 secured to the engine nosing |12. A ring gear 2|0 is provided with a lever 2|2, and a control cable or rod 2|4 outside of the cover |80, engages pinions 2 I6 fixed to the ends of the control shaft 200, so that oscillation of the lever 2|2 rotates the screw shaft 200 and causes axial movement of the control ring |98 within the regulator. The flange 202 is prepared with a toothed periphery 2|1 to engage a pinion 2|8 that drives the pump I0. When the propeller is in operation, it will be observed that the control ring |98, the screw shafts 200, the sleeve 204 with its attached spur gear 2|1 are all non-rotative because of the interengagement provided by 206 and 208, which means that the propeller with the regulator containing the control apparatus rotates outside of this group of elements, known as an adapter assembly. The pump gear 2|8 rolling over the spur 2|1 effects development of pressure by the pump |0 within the lines |4 and 10 of the system which pressure is regulated by the three element pressure control valve and delivered to the governor engagement. The relation .of these working arms may be altered by actuating the arm 2 l2 of the ring gear which in turn effects the shifting of the control ring 198 and consequently moves the carriage 32 along the ways 92 substantially as shown and described in the patents to Blanchard. etal. 2,367,151 and 2,307,102.

During on-speed operation, the land I8 of the governor valve will so cooperate with the port 38 as to result in equal forces being applied to both sides of the piston 150 of the blade motor 52, as a consequence of which there will be no blade shift movement. In the present instance, because of the natural tendencies of the blade while in operation to seek a decreased pitch position, theparticular coincidence of governor lands and ports during on-speed will involve a slight amount of predetermined offset as designated at Y in Fig. 1. That particular predetermined offset takes into account tlce tendency of the blade to Amove to decreased pitch position, and permits an exactly balancingr force of hydraulic pressure tobe applied to the chamber 46 of the blade motor for opposing the built in tendency of decreased pitch shift. The off-set also maintains a 4continual flow from the pressure line i4 thru the passage H4 and has been described to exit at'the constant leak orifice 66. Upon the occurrence of increase in speed the governor Valve moves outwardly, upward as shown in Fig. 1, which lincreases the yopening of the increased pitch port and allows sufficient pressure application to the passage 42 and the chamber 46 to move the piston 50 for increasing the pitch of the blade 60 for effecting the increase in the load placed upon the motor and consequently reflecting in a decrease of speed, inthe meanwhile the chamber 4B draining thru the passages 44 the `pressure relief valve chamber |63 to return to the reservoir. Upon the occurrence of decrease in propeller speed, less centrifugal force is applied to the governor Valve by reason of which the kspring 34 moves the governor Valve plunger inwardly, first, such as to vcompletely cover the increased pitch port 38, or so as to absorb the off-set Y. That shift in itself so disturbs the balance of forces applied to the chambers 46 and 48 as to'allow blade 6i) to shift toward the decreased pitch position against the removal of pressure application that has been t'heretofore exerted in 46. If that release of opposing pressure thru the passage 42 that is afforded by means of the constant leak orince |60 is-insuflicient to provide enough correction, then further inward movement of the governor valve plunger opens the increase pitch port 38 to drain. Inorder to restrict the rapidity of drain from the chamber 46, the governor valve provides an annular groove 226 between the land I8 and a third land 222 adjacent the increased pitch port 33. An axial bore 224 and a cross port 226 opens the channel to the outer end of the governor valve, such that when the increased pitch port 38 is exposed to drain, flow therefrom is restricted to that of a quantity that will prevent hunting or speed variation from the adjusted speed level. Thus, in draining from the chamber 46 thru the port 38 the hydraulic iiuid must pass thru the restricted port 226 and thence thru the axial bore 224, all as is more amply described and claimed in the "copending application filed by me on October 8, 1945, as Ser. No. 621,004.

The operation of the disclosed system as effected yby the three element pressure control valve and thexpressure relief valve is as follows: the

lili

constant-leak valve CLV maintains a constant leak from the increased pitch port 38 as long as the line is open to the valve with a pressure of as much as 200 lbs. p. s. i. This leak is produced by the valve maintaining a constant pressure of 200 p. s. i. against the orifice |60. In the preferred embodiment the amount of flow through this orifice at 200 p. s. i. is approximately 60 cubic inches yper minute, which in the said preferred embodiment is equivalent to about 1 per second rate of pitch change. The equal-area valve EAV maintains the approximate position shown in the sketch during normal operation, or during the ecuilibrium position as it is sometimes referred to, and controls the pump operating pressure, maintaining it at afixed amount above the pressure at the increase pitch port 38. 'Ihe equal area valve closes only when the governor valve GV is wide open at the control port calling for the full available rate of pitch change, which happens only Yin extreme cases, such as during feathering and braking operations. When the equal-area valve EAV closes, the line from the increase pitch port 38 to the leak valve CLV is shut off at H8, from .which it will appear that the leak valve CLV does not interfere with the maximum rate of pitch change and flow-sensitive feathering systems. The vpressure relief valve RV limits the system pressure and operates only in extreme cases where the equal-area valve EAV may be cverdamped. The amount of offset of control land and port designated at Y in Fig. l, is large enough to supply the constant leak and maintain the required pressure against the ever present blade load tending to decrease pitch. If an overspeed occurs, the distance Y increases supplying more flow which increases the blade angle. If an underspeed occurs, the distance Y decreases reducing the supply to the leak valve CLV which decreases the blade angle. Since the leak valve CLV is producing a constant leak the blade angle decreases at the rate of the difference in the constant leakand the amount of iiow being supplied thru the governor GV.

The governor valve GV now becomes a true flow governor. The approximate 1 per second rate of decreased pitch is adequate to take care of normal operation in the described embodiment which includes the usual maneuvers within the operating range ofthe pursuit plane. The governor GV only throttles oil thru the increase pitch port -38 during normal operation. All reversing flow forces are removed from the governor valve and the constant pressure difference from the pump line I4 to the increase pitch line 42 is controlled by the load of the spring- 96 in the equal-area valve EAV, which can be kept to areasonable amount for controlling the one flow force now left in the governor GV during normal operation. Since the equal-area Valve EAV maintains a constant pressure drop across the governor the most ideal porting for a Vgiven installation can be obtained. The equal-area valve EAV gives the system maximum pressure sensitivity as Well as produces the ideal constant pressure difference between pump i0 and increased pitch line d2. High pressure sensitivity is needed because of the friction effect of the blade motor unit 5U, 52.

While the embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. A fluid pressure system including a fluid motor working against Widely varying opposing forces, a fluid pressure source, a governor valve with a flow port connected to one side of said fluid motor, and automatically operable to distribute pressure fluid from said source to the fluid motor for operating the fluid motor in one direction, said port when the fluid motor is inactive being open to source pressure by a predetermined amount, means including a pressure reducing valve connecting said pressure source to the other side of said fluid motor tending to operate said motor in the opposite direction, pressure control means including a leak orifice, and a valve for controlling the flow of fluid from the orifice to match the flow from said governor port, said orifice control valve having an area exposed to the source pressure tending to move the valve in a pressure reducing direction, an equal area exposed to the pressure at the governor flow port tending to move the valve in a pressure increasing direction, spring means assisting the valve movement toward pressure increase, a flow control valve opening to said leak orifice and having a passage controlled by said orifice control valve, pressure increasing movement of said orifice control valve tending to close the passage to the flow control Valve, and operating upon wider governor port opening to increase the source pressure commensurate with the demands of the force to be opposed by said fluid motor.

2. A fluid pressure system including a fluid motor working against widely varying opposing forces, a fluid pressure source, a governor valve with a flow port connected to one side of said fluid motor, and automatically operable to distribute pressure fluid from said source to the fluid motor for holding the fluid motor inactive and for operating the fluid motor in one direction, means applying reduced source pressure to the other side of said fluid motor, said governor flow port when the fluid motor is inactive being open to source pressure by a predetermined amount, pressure control means including a leak orifice, and a valve for controlling the flow of fluid from the orifice to match the flow from said governor flow port, said orifice control valve having one area exposed to the source pressure for moving the valve in a pressure decreasing direction, an opposed equal area exposed to the pressure at the governor flow port for moving the valve in a pressure increasing direction, a port and passage leading to said leak orifice and controlled by said valve movement, a flow control valve in the passage to said orifice responding to the flow through the associated port of the orice control valve for effecting a substantially constant leak from said orifice, said orifice control valve operating upon decrease of governor port opening to increase the fluid flow to said leak orifice.

3. In a fluid pressure system for actuating a fluid pressure motor to adjust the pitch of blades on aircraft propellers, through a Wide range of angles, comprising in combination, a source of fluid pressure for application to said fluid pressure motor, a flow governor connected to said source of fluid pressure for directing .pressure fluid from said source to one side of the fluid pressure motor for holding the motor inactive and for actuating the motor in opposite directions, said governor having a port connected to one side of said motor, and which port is partially open upon inactive status of said motor, valve means having nite orifice and a pressure responsive Valve pro-y viding a selectively operable constant leak of predetermined magnitude from said governor port, and subject to the control of said first mentioned valve, passage means supplying fluid to said orice and said pressure responsive valve from said first-mentioned valve and valve means providingdiminished source pressure on the opposite side of said motor for opposing the governor directed pressure.

4. In a fluid pressure system for actuating a fluid pressure motor to adjust the pitch of blades on aircraft propellers, through a Wide range of angles, comprising in combination, a source of fluid pressure for application to said fluid pressure motor, a flow governor connected to the source of fluid pressure for directing pressure fluid from said source to one side of the fluid pressure motor for holding the motor inactive against the ever present tendency to move to decrease pitch, and for actuating the motor in one direction for increasing the pitch of the blades, said flow governor having a control port connected with one side of said motor, a pressure reducing valve connecting the other side 0I said motor with the said source of fluid pressure, a pressure control unit for controlling the potential of pressure applied to said one side of the motor and including a spring-biased valve for controlling the potential of .pressure source as needed at said governor control port, opposite surfaces of said valve being exposed to the source pressure and to the pressure at the control port of said governor for maintaining the pressure of said source, a leak oriflce and a controlling valve therefor operatively associated with said pres-- sure control valve maintaining a selectively operable constant leak from the control port of the governor, flow of pressure fluid to the said control valve being under the control of the said pressure control valve, and a relief valve connected at all times to the potential of the source pressure for limiting the potential thereof to a safe value.

5. In a fluid pressure system for actuating a fluid pressure reversible motor subject to a, widely variable load applied continuously to one side of the motor, the combination comprising, a source of fluid pressure, a flow governor connected with the source and having a single flow port connected with said motor to oppose the variable load, means connected with said source pressure providing a constant reduced pressure applied to the motor in aiding relation to the variable load, and means controlling the pressure applied through the flow port of said governor to hold the motor inactive by a balance of forces on opposite sides thereof, or to actuate said motor in either load aiding relation or load opposing relation, said controlling means including a partial opening of said flow port admitting source pressure to the load opposing side of said motor, a variable pressure control valve controlling the source pressure applied through said flow port, said valve having an area constantly exposed to said source pressure and an equal opposed area constantly exposed to the said flow port whereby a predetermined pressure drop is maintained across said flow port, and a constant leak device controlled bythe opposing pressures onthe pressure control Valve for equalizing the `source pressure Vapplied by the ow port tothe motorwith the combined effects ofthe load and constant reduced pressure applied to the other side of the motor for retaining the motor in 'an inactive position.

6. The combination set forth in claim 5, wherein lincreased opening of the governor floW port for actuating the motor in load opposing .relation operates to increase the source pressure without changing the amount of `leak fromthe system-and without altering the constant reduced pressure applied to the motor in aiding relation to the load on the motor, said leak device including an orifice and flow control valve connected with the pressure control valve and establishes a constant leak from the system equal to the constant pressure at the governor flow port.

'7. In a uid pressure system for advancing, retarding and holding a reversible piston motor against an ever present and widely varying load, comprising in combination, a source of uid pressure, a governor Valve connected With said source and having a single ilow port for directing pressure fluid from said source to the advancing side of said motor, means including a pressure reducing valve for applying iiuid pressure of relative low potential to the retarding side of said motor, means regulating the source pressure applied to the advancing side of said motor and to said pressure reducing valve and including a valve having opposed equal areas, one of which is exposed continuously to the source pressure and the other area of which is continuously exposed to the pressure at said governor ilow port, means including a port controlled by the valve having equal opposed areas providing a constant leak from the system, and means including a predetermined opening of the flow port for balancing the governed high pressure applied to the advancing side of the motor against the aggregate of variable load and reduced pressure applied to the retardingI side of the motor, such that the motor may be held inactive, normal operation of the governor valve in opposing varying loads effecting a change in opening of the said flow port with a resultant change in governed pressure by the valve of equal areas without change of the constant leak from the system or change of reduced pressure applied by the pressure reducing valve.

8. The combination set forth in claim 7, Wherein said pressure reducing valve provides a port for drain of the retarding side of the motor when the flow port of the governor applies governed high pressure to the advancing side of the motor in excess of the agg-regate reduced pressure and variable load applied to the retarding side of the motor.

9. The combination set forth in claim 7, wherein said governor valve provides a restricted outlet open to said flow port for drain of the advance side of the motor when the governor valve cuts off application of governed high pressure to the motor, and the aggregate of varying load and reduced pressure applied to the retarding side of the motor dominates.

l0. A uid pressure system including a fluid motor working against opposing forces of widely varying magnitude, a iluid pressure source, a distributor valve automatically operable to distribute pressure fluid from the source to one side of the iluid `motor for just balancing the opposing forces on the motor, and a pressure control means operatively connected to 'the pressure source and to the fluid motor formaintaining 'a denite pressure vdifferentialbetween the Vpressure source and the pressure distributedtoone side Vof the fluid motor, said pressure control means including aconstant leak orifice Variably connectible -to the distributed pressure, a pressure control valve having equal opposed areas one subject to the'pressure source and the other subject to the pressure distributed to said'one side of the lluid motor, `said leak voriflcebeing controlled by a 4valve open at all times tothe pressure distributed to said one side of the `fluid motor, said orifice control valvebeing responsive to `apredetermined pressurerise in the motor-to stop all now through said orifice, and a valve unit for reducing the pressure applied to the other side of said fluid motor.

11. A fluid pressure system including, a fluid motor having a movable member subject to an external force tending to move the member in one direction, a source of uid pressure, a pressure reducing valve connected to said source and said motor for applying fluid under reduced pressure to one side of the motor member in assisting relation to said external force, a control Valve automatically operable to apply pressure uid from said source to the other side of the motor member in opposing relation to said external force for just balancing the combined effects of said external force and reduced fluid pressure while the motor is inactive, and pressure control means operatively connected with said source and said other side of the motor member for maintaining a definite pressure dierential between the source of fluid pressure and the pressure of the fluid applied to said other side of the motor member, said pressure control means including a constant leak orifice connected to the pressure fluid applied to said other side of the motor member and operable only when pressure fluid is applied to said other side to maintain a continual flow of fluid to drain, and a pressure control valve having equal areas subject to the pressure of said source and the pressure of the iluid applied to said other side of the member for controlling the flow from said leak orice.

12. The combination set forth in claim 11 wherein the pressure control valve controls a drain port from the pressure source by reason of resilient mechanism tending to close said drain port, said area of the valve exposed to source pressure opposing the resilient mechanism tending to close said drain port, and said area exposed to the pressure applied to said other side of the motor member assisting the resilient mechanism tending to close the drain port.

13. The combination set forth in claim 11 wherein the control valve includes a land, a port connected with the other side of said motor member and cooperating with said land, said land and port being off-set in non-coincidence a predetermined amount lengthwise along a sleeve encompassing said control valve for establishing the now of fluid from the pressure source through said port to said one area of the pressure control valve exposed to the pressure distributed to said other side of the motor member and to said leak orice.

14. A uid pressure system including, a fluid motor having a movable member subject to an external force tending to move said member in one direction. a source of iluid pressure, a governor valve having a flow port connected to one side of the uid motor, a pressure reducing valve connected to said source for reducing the pres-- sure of fluid applied to the opposite side of the fluid motor, said governor valve being automatically operable to distribute pressure fluid from said source to said one motor side for opposing the reduced pressure applied to the opposite motor side, said reduced pressure acting in assisting relation to said external force, the construction and arrangement being such that the fluid motor will be held inactive, While said oW port s slightly open to said source, and pressure control means connected between said port and said source including a constant leak orice connected to said governor valve iiow port and operable only when pressure fluid flows through said flow port to the motor to maintain a continual flow of fluid to drain, and a valve for Varying the quantity of Iiow to said leak orifice.

RICHARD E. MOORE.

References Cited in the file 0f this patent UNITED STATES PATENTS 

